Persistent Laryngospasm

[DeepSeaDan]

Good Physicians,

The Scenario:

A diver panics at depth ( let us say 60 fsw ), rejects the regulator, inhales some water, laryngospasms, loses conciousness & dry drowns. They are recovered to surface :2 post-incident in a "chin-up" manner.

Question: Is it likely this casualty would suffer "persistent laryngospasm" which would act as an airway obstruction & cause lung baratrauma en route to the surface?

Thanks,
DSD

 

[TSandM]

It is possible, but I would think it somewhat unlikely. Losing consciousness from hypoxia should result in loss of the gag reflex and relaxation of the laryngospasm, and in addition, OUTWARD force can often open the vocal cords where attempts at inspiration, which tend to pull the cords together, cannot. Positive pressure ventilation can often overcome laryngospasm, as well.

 

[HBO MD]

I agree with TSandM.
Just as all bleeding ultimately stops, once a patient lapses into unconsciousness, the laryngospasm should no longer persist. Hence the ability to intubate, and hopefully resuscitate at this point.

 

[doctormike]

Here's my input, from the ENT perspective:

Laryngospasm is an odd and poorly understood phenomenon. As you all know, the main function of the larynx is not speech, but to keep us from drowning in our own saliva and whatever we eat. In human beings (and in other land mammals), the air and food passages cross, so we need a fancy system of reflexes to close the airway during swallowing. Dolphins have a "better" system, in that they just have the airway routed completely away from the food pathway (although that does require a pretty reliable sphincter at the blowhole to keep the ocean out of their lungs).

In some cases (lightly anesthetized patients, some newborn infants, etc..) this reflex closing of the vocal cords gets switched on full blast, and doesn't let up as it is supposed to. In the OP's question, the normal reaction (laryngeal adduction, or closing of the vocal cords) happens in response to a stimulation (a little bit of the Caribbean sea hitting the larynx). Laryngospasm is what happens when this normal response doesn't stop... if there is no air (i.e. regulator lost or rejected), it is sort of a moot point whether the vocal cords are closed or open, but assume that there is persistent laryngospasm which would cause hypoxia even if the regulator was replaced.

Laryngospasm will continue until one of three things happens:

1) it is "broken" by paralyzing drugs or positive pressure mask ventilation - in the case of anesthesia

2) it stops on its own, as the higher brain functions gain control over the more primitive laryngeal reflexes

3) the patient becomes unconscious from lack of oxygen, and eventually muscle function relaxes (on the way to death).

It is not clear why otherwise normal patients can sometimes develop laryngospasm - there may be an emotional component, allergies, reflux, etc... But I HAVE seen a patient who underwent an emergency tracheotomy for this..!

And finally, getting back to the OP question - barotrauma. The question is which is stronger: the force of expanding air in the chest pushing its way out of the lungs through the larynx in spasm, or the muscles of the larynx holding it in.

Since we are all taught not to hold our breath on ascent in our open water classes, that implies that it IS possible to hold in enough pressure to cause barotrauma. I don't see why the force of laryngospasm in an unconscious patient would be theoretically less than the force of laryngeal adduction in conscious breath holding... so I would have to assume that barotrauma would be a consideration if you could successfully resuscitate the patient on the surface...

I guess the real question is whether or not laryngospasm is still happening on ascent. If you waited long enough, yes eventually the larynx would open. But if the diver was being taken to the surface earlier in this process, then it might still be closed...

Interesting question!

Mike

 

[mikerault]

So stuffing the reg back in their mouths and doing a purge (just a short burst) should clear it?

 

[doctormike]

So stuffing the reg back in their mouths and doing a purge (just a short burst) should clear it?

I assume that you mean positive pressure ventilation to break laryngospasm? An interesting idea in theory, but remember:

1) you would have to diagnose laryngospasm - not so easy for a trained anesthesiologist on dry land in an operating room, not sure how you would do it at all underwater.

2) You would have to make sure that there was a tight seal, otherwise air would just leak out around the reg - since we are talking about an unconscious patient, they won't be able to help you. Also, the pressure would probably vent out around the mask seal unless you were also clamping that on the face tightly...

3) The regulator is designed to deliver pressure at ambient pressure, so you really aren't giving much positive pressure at all. You get airflow because you are inhaling through the regulator, so the airstream is driven by the relative negative pressure in your lungs, as compared to the ambient pressure. Pushing the button does give a burst of relatively positive pressure. However, it is really designed to be enough to clear the circuit, probably not as much as you could generate with an ambu bag and face mask (which is used to break laryngospasm in the operating room, with the popoff valve cranked down to get higher pressures...).


Mike

 

[mikerault]

I was thinking more in the case of when it happens to you...either at dpeth or on the surface in rough water. Anyway, interesting discussion.

Mike

 

[doctormike]

I was thinking more in the case of when it happens to you...either at dpeth or on the surface in rough water. Anyway, interesting discussion.

Mike

Yes, it is an interesting discussion!

I think that if you were awake enough to remember to push the purge button, you would be awake enough to abduct (open) your vocal cords...

Remember, this is a primitive protective laryngeal reflex that causes the vocal cords to snap shut in response to some stimuli (your larynx is constantly protecting you from drowning in your own secretions, or the occasional dry martini). It can almost always be overruled by voluntary efforts, input from the higher centers in the brain.

Laryngospasm mainly happens in people with altered degrees of consciousness - notably light anesthesia. It can sometimes happen with severe stimulation (such as smoke inhalation), but as long as the larynx is not physically obstructed (as in a burn injury with swelling, allergic reaction, etc..), a calm breath will take care of things. So - as with most diving emergencies - the number one rule is not to panic...

Mike

 

[mikerault]

I don't know, it gets a bit dramatic for a few seconds when you are just sitting in your living room and "swallow wrong" now if that were to happen at depth or even on the surface it could be quite bad.

Mike

 

[DeepSeaDan]

...for contributing to this discussion ( my question's genesis is a point made in a "Rescue" thread over in the Advanced Diving section ).

Now, what about the time frame? Any suggestions as to how long one might remain in spasm after loss of conciousness? Further; I've queried several doctors on the subject of cardiac sustainability after cessation of respiration, & have received a variety of estimates. Would anyone care to speak to that issue? Lastly, how imperative is the "chin-up" posture for the patient's head when ascending during a rescue of an unresponsive diver? I have read one opinion where the author opined that pulmonary air will escape regardless of the patient's head position because of Boyle's Law, though this seems to run contrary to conventional wisdom as I understand it.

Thanks again!

DSD